FR3115341A1 - Screw connection for rocket engine - Google Patents

Abstract

Screw connection for rocket engine Connection (10) of a pipe (50) to a support (20), comprising a joint (14) secured to the support (20), a joining part (12) configured to cooperate with the joint (14) by clamping, and an arm (16) extending around the conduit (50) external to the conduit (50), connecting the conduit (50) to the joint portion (12), wherein the joint portion (12 ) has a stiffness greater than that of the arm (16) and the seal (14). Figure for abstract: Fig. 2.

Description

Screw connection for rocket engine

This disclosure relates to a rocket engine screw connection configured to join a fluid line to another element of the rocket engine.

1. Assurer une étanchéité à des températures allant des températures cryogéniques à des températures supérieures à la température ambiante.
2. Résister à des conditions vibratoires importantes.
3. Conserver leur étanchéité lorsque la conduite et/ou le raccord vissé se déforme.

The use of screw connections in a rocket engine is common. These screwed connections must comply with demanding specifications and must in particular:

1. Provide a seal at temperatures ranging from cryogenic temperatures to temperatures above ambient.
2. Withstand strong vibration conditions.
3. Maintain their tightness when the pipe and/or the screwed connection becomes deformed.

Furthermore, the screwed connection must maintain its performance during the transitional regimes of the rocket engine, regimes in which the temperature and vibration conditions change.

Certain known screw connections make it possible to meet these specifications at least partially, among them the screw connection commonly referred to by the acronym “RLSEP” and the screw connection with seals commonly referred to by the acronym “VSEP”. These two types of fittings are particularly expensive.

On the other hand, other screwed connections comprising flat seals are known, but do not make it possible to satisfy the specifications set out above. In particular, flat gaskets have the disadvantage of creeping at room temperature. Their use requires maintenance prior to each use of the engine containing them, which is prohibitive.

There is therefore a need for cost reduction and improvement of known devices.

The present disclosure relates to a screw connection of a fluid pipe to a support, comprising a joint secured to the support, a joint part configured to cooperate with the joint by clamping, and an arm extending around the pipe at the exterior of the pipe, connecting the pipe to the joint part, in which the joint part has a stiffness greater than that of the arm and the joint.

Thus, such a screwed connection has an arm which is capable of bending to reduce the stresses imposed by the expansions and compressions undergone by the connection under the effect of temperature. Therefore, this screw connection is usable over a wide temperature range. In particular, such a screw connection can be used over a wider temperature range than known screw connections.

Furthermore, this configuration is able to withstand the vibratory stresses which may be experienced in a rocket engine. In general, this screw connection is compatible with the transient regimes of the operation of the rocket engine and is capable of withstanding rapid temperature variations.

Also, the screwed fitting described above is simple to manufacture, and in particular simpler to manufacture than the known RLSEP and VSEP fittings. It is therefore less expensive. In general, the screw connection of this disclosure is inexpensive.

In certain configurations, the threaded connection comprises a first threaded part and the support comprises a second threaded part, the first threaded part and the second threaded part being configured to cooperate to assemble the connection to the support by screwing.

In some configurations, a portion of the joint portion is configured to yield when fluid passes through the conduit.

In this configuration, the tightness of the screw connection is improved. Plasticization takes place during the passage of the cryogenic fluid, and results in the creation of a plasticized zone which improves the seal.

In certain embodiments, the joint has a greater stiffness than that of the arm.

In this configuration, the arm is the first element that flexes when a stress is applied to the screw connection. Since the arm is the most flexible part of the fitting, the fitting is then able to more easily absorb the stresses it undergoes.

In some embodiments, the carrier is another conduit.

In this configuration, the screw connection can be used in a greater number of situations, and thus be included in a greater number of pipes, thereby reducing the manufacturing cost of the rocket engine.

In some embodiments, the gasket is copper.

The copper has properties making it possible to guarantee a rigidity of the joint part compatible with the rigidity of the joint and of the support during the steady state and the transient states.

This configuration is also advantageous because the copper does not flow at room temperature. Thus, a screw connection that is assembled and then stored does not lose tightness due to gasket creep, since the latter does not creep. In particular, the ratio between the mounting and storage temperature and the copper melting temperature is less than 0.25, a value above which creep phenomena may appear. In this case, this same ratio is 0.31 for aluminum seals, which makes the creep of an aluminum seal possible and requires regular retightening.

In some embodiments, a sealing volume is provided between the pipe on the one hand and the joint and the joint part on the other hand, the sealing volume being configured to collect the fluid escaping from the joint between the first threaded part and the second threaded part, said threaded parts typically not having the function of providing a sealed connection.

In this configuration, the sealing volume makes it possible to contain the fluid escaping from the permeable thread in the sealing volume.

In some embodiments, the seal and the seal portion are annular.

In some embodiments, the joint portion includes an annular sealing projection extending from a face of the joint portion configured to contact the joint, and configured to penetrate the joint upon tightening of the part. joint on the joint.

This configuration provides an additional element to seal the connection. Sealing is then ensured by the projection and by the tightening of the joining part against the gasket.

The presentation also relates to a rocket engine comprising one of the screw connections described above.

Thus, said rocket engine comprises the aforementioned advantages, namely lower cost and increased reliability.

In certain embodiments, the rocket engine comprising said screw connection sees this connection arranged in a cryogenic line.

The presentation also relates to a spacecraft comprising a rocket engine as described above.

The invention and its advantages will be better understood on reading the detailed description given below of various embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended figures, on which:

The shows a spacecraft comprising a screw connection according to one embodiment.

The shows a sectional view of a screw connection according to a first embodiment.

FIG. 3A represents a partial cross-sectional view of an unassembled screw connection according to the first embodiment, FIG. 3B represents a partial cross-section view of an assembled screw connection according to the first embodiment of a pipe in which no fluid has passed, FIG. 3C represents a partial sectional view of a screw connection according to the first embodiment when the rocket engine is in transient state and when a cold fluid passes through the pipe, FIG. 3D represents a partial view in section of a screw connection according to the first embodiment when the rocket engine is in transient state and when a hot fluid passes through the pipe.

FIG. 4A represents partial cross-sectional view of an unassembled coupling according to a second embodiment, FIG. 4B represents partial cross-sectional view of an assembled coupling according to the second embodiment.

The schematically represents a spacecraft 500 comprising a rocket engine 80, itself comprising a screwed connection 10. The screwed connection 10 is arranged within a pipe 50 shown partially in FIGS. 2 to 3.

The represents a screw connection 10 according to a first embodiment. This screwed connection (or connection) 10 comprises a first threaded part 11, a joining part 12, a seal 14 and an arm 16. The connection 10 is secured to the line 50, and the latter extends along an axis X. This presentation takes the non-limiting example of a cryogenic line 50, but the pipe is capable of conveying other types of fluid.

The arm 16 is secured to the pipe 50 while the seal 14 is secured to a support 20. The arm 16 extends from the outer periphery of the pipe 50, and has a generally annular shape. The arm 16 is configured to deform elastically under the expected conditions of use of the screw connection 10.

The support 20 comprises a second threaded part 21 and the first threaded part 11 of the coupling 10 is configured to cooperate with the second threaded part 21 of the support 20. The support 20 can moreover be another fluid pipe or an element of the motor- rocket. In the example of the first embodiment, the support 20 is a part of the rocket engine secured to the pipe 50 through the cooperation of the first threaded part 11 and the second threaded part 21.

A sealing volume 18 is provided between the pipe 50 on the one hand and the seal 14 and the joining part 12 on the other hand. In the example of the first embodiment, the sealing volume 18 is covered by the arm 16 from above and by the support 20 from below.

Arm 16 and joint portion 12 of connector 10 may be supplied in one piece with pipe 50.

During the assembly of the connector 10 with the support 20 by cooperation of their respective threaded part 11, 21, the joining part 12 is tightened against the joint 14, which ensures sealing.

The gasket 14 is typically an annular element with an interior radius greater than 5 mm and less than 15 mm, preferably less than 10 mm, and an exterior radius greater than 16 mm and less than 25 mm, preferably greater than 20 mm. The seal 14 is for example made of copper or a copper-based alloy, that is to say an alloy whose largest mass fraction is copper.

The joint part 12 is for example annular, made of stainless steel and has dimensions compatible with its tightening on the joint 14.

Figures 3A-D show fitting 10 in different states.

FIG. 3A represents a coupling 10 before the screwing of the first threaded part 11 into the second threaded part 21. It can be seen that the arm 16 is not bent.

FIG. 3B shows a connector 10 in which the first threaded part 11 is screwed into the second threaded part 21, such as could be obtained just after screwing or after storage. No fluid flows in line 50. It can be seen that arm 16 is slightly bent, so that seal 14 is tighter. This bending of the arm 16 is elastic. In particular, the seal 14 is slightly plasticized. Thus, a fitting 10 screwed on and then stored retains its tightness.

FIG. 3C represents a screw connection 10 of a pipe 50 through which cold fluid passes, while the connection 10 is in a transient thermal state. It can be seen that the arm 16 flexes more significantly compared to its flexion under the conditions of FIG. 3B. This flexion of the arm 16 remains elastic. Consequently, the seal 14 is tighter.

FIG. 3D represents a screw connection 10 of a pipe 50 through which a hot fluid passes, while the connection 10 is in a transient thermal regime. In this situation, the pipe 50 expands, which lowers the flexion of the arm 16: that is to say, it tends to return to a position in which it is not constrained, with respect to its flexion at the conditions of Figure 3B, while remaining flexed. This deflection of the arm 16 remains elastic. However, the connector 10 retains its tightness and the joint part 12 remains tight against the joint 14. Indeed, the deflection of the arm 16 is less than its deflection at rest, when no fluid passes through the pipe 50. The arm 16 therefore remains bent even when the pipe is traversed by a hot fluid. Thus, the joint part 12 remains in contact with the seal 14.

Figures 4A and 4B show a connector 10 according to a second embodiment, respectively disassembled and assembled. This coupling 10 comprises a joint part 12, a joint 14 and an arm 16. The coupling 10 of the second embodiment comprises an annular projection 13 placed on the joint part 12. This projection 13 is placed on one face of the part of joint 12 configured to be in contact with the joint 14 and to penetrate it according to the direction of screwing of the connection 10. Thus, the projection 13 improves the tightness of the screwed connection 10.

Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different illustrated/mentioned embodiments can be combined in additional embodiments. Accordingly, the description, dimensions and drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a method.

Claims (10)

Screw connection (10) of a fluid pipe (50) to a support (20), comprising a joint (14) secured to the support (20), a joint part (12) configured to cooperate with the joint (14) by clamping, and an arm (16) extending around the pipe (50) outside the pipe (50), connecting the pipe (50) to the joining part (12), wherein the part of joint (12) has a stiffness greater than that of the arm (16) and the joint (14). A screw connection (10) according to claim 1, wherein the joint (14) has a greater stiffness than the arm (16). Screw connection (10) according to one of Claims 1 or 2, in which the support (20) is another pipe (50). Screw connection (10) according to one of Claims 1 to 3, in which the seal (14) is made of copper. Screw connection (10) according to one of Claims 1 to 4, in which a sealing volume (18) is provided between the pipe (50) on the one hand and the seal (14) and the joint part (12 ) on the other hand, the sealing volume (18) being configured to collect fluid having leaked from the pipe (50). Screw connection (10) according to one of Claims 1 to 5, in which the joint part (12) and the joint (14) are annular. Screw connection (10) according to one of claims 1 to 6, in which the joint part (12) comprises an annular sealing projection (13) extending from a face of the joint part (12) configured to enter in contact with the joint (14), and configured to penetrate the joint (14) when tightening the joint part (12) on the joint (14). A rocket engine (80) comprising a screw connection (10) according to any one of claims 1 to 7. A rocket engine (80) according to claim 8, wherein the screw connection (10) is disposed in a cryogenic line. A spacecraft (500) comprising a rocket engine (80) according to claim 9.